The present invention relates to an exhaust gas recirculation device of an engine, and more particularly to an exhaust gas recirculation device of en engine including inline-multi cylinders in which a recirculated exhaust gas is supplied to intake ports for engine cylinders.
In the exhaust gas recirculation device of an engine including inline-multi cylinders, an exhaust gas recirculation device which is , for example, a so-called “port EGR” is used for engines formotor vehicles or the like, in which the exhaust gas derived from an exhaust passage of the engine is supplied to intake ports of the engine via diverged exhaust gas recirculation passages so as to provide the exhaust gas into respective cylinders equally. As an exemplary of such “port EGR”, the following device is known. Namely, in the exemplary device, there is provided a plate member for EGR (Exhaust Gas Recirculation) which is interposed between an intake port flange of a cylinder head and an intake manifold, and this plate member and the intake port flange portion jointly constitute a tournament-type of exhaust gas recirculation passage (EGR passage) for respective intake ports of plural engine cylinders which is comprised of a common passage portion, an upstream diverged passage portion and a downstream diverged passage portion. Further, an additional device which comprises cooling ribs which are provided at a periphery of such palate member is also known (see, for example, Japanese Patent Laid-Open Publication No. 2002-339809).
Meanwhile, for engines for motor vehicles or the like, an engine cylinder head made from aluminum is common, and an intake manifold made from resin is also common in order to further a weight reduction of the engine. Herein, in the event that such intake manifold made from resin is applied to the engine including inline-multi cylinders in which there is provided the above-described plate member interposed between the intake port flange of the cylinder head and the intake manifold to provide the port EGR, there exists the following problem. Namely, in general, the intake manifold made from resin has a heat resistance of approximately 120° C., but a gas temperature of the exhaust gas derived from the cylinder head to the plate member is approximately 150° C. Accordingly, the intake manifold made from resin may have a problem of its durability unless proper measures is taken because it receives an excessive-heat influence from the plate member.
Also, in the above-described device of the prior art, in which the upstream and downstream diverged passage portions are formed within the plate member and the common passage portion is formed at the intake port flange portion, the intake port flange portion needs to be relatively large in order to provide the common passage portion of thereat, resulting in a restriction in designing the cylinder head. Accordingly, it would prevent the engine from being compact. Further, constituting such exhaust gas recirculation passages over the plate member and the intake port flange portion would restrict proper designing of the exhaust gas passage.